Tocopherol as treatment for lung injury associated with burn and smoke inhalation

The Angiotensin-converting enzyme inhibitor captopril inhibits poly(adp-ribose) polymerase activation and exerts beneficial effects in an ovine model of burn and smoke injury

We investigated the effect of the angiotensin-converting enzyme (ACE) inhibitor captopril in a clinically relevant ovine model of smoke and burn injury, with special reference to oxidative stress and activation of poly(ADP-ribose) polymerase, in the lung and in circulating leukocytes. Female, adult sheep (28-40 kg) were divided into three groups. After tracheostomy and under deep anesthesia, both vehicle-control-treated (n = 5) and captopril-treated (20 mg/kg per day, i.v., starting 0.5 h before the injury) (n = 5) groups were subjected to 2 × 20%, third-degree burn injury and were insufflated with 48 breaths of cotton smoke. A sham group not receiving burn/smoke was also studied (n = 5). Animals were mechanically ventilated and fluid resuscitated for 24 h in the awake state. Burn and smoke injury resulted in an upregulation of ACE in the lung, evidenced by immunohistochemical determination and Western blotting. Burn and smoke injury resulted in pulmonary dysfunction, as well as systemic hemodynamic alterations. Captopril treatment of burn and smoke animals improved PaO2/FiO2 ratio and pulmonary shunt fraction and reduced the degree of lung edema. There was a marked increase in PAR levels in circulating leukocytes after burn/smoke injury, which was significantly decreased by captopril. The pulmonary level of ACE and the elevated pulmonary levels of transforming growth factor β in response to burn and smoke injury were significantly decreased by captopril treatment. Our results suggest that the ACE inhibitor captopril exerts beneficial effects on the pulmonary function in burn/smoke injury. The effects of the ACE inhibitor may be related to the prevention of reactive oxygen species-induced poly(ADP-ribose)polymerase overactivation. Angiotensin-converting enzyme inhibition may also exert additional beneficial effects by inhibiting the expression of the profibrotic mediator transforming growth factor β.

Burn and smoke injury activates poly(ADP-ribose)polymerase in circulating leukocytes

The nuclear enzyme poly(ADP-ribose)polymerase (PARP) plays a significant role in the pathogenesis of various forms of critical illness. DNA strand breaks induced by oxidative and nitrative stress trigger the activation of PARP, and PARP, in turn, mediates cell death and promotes proinflammatory responses. Until recently, most studies focused on the role of PARP in solid organs such as heart, liver, and kidney. We investigated the effect of burn and smoke inhalation on the levels of poly(ADP-ribosylated) proteins in circulating sheep leukocytes ex vivo. Adult female merino sheep were subjected to burn injury (2× 20% each flank, 3 degrees) and smoke inhalation injury (insufflated with a total of 48 breaths of cotton smoke) under deep anesthesia. Arterial and venous blood was collected at baseline, immediately after the injury and 1 to 24 h after the injury. Leukocytes were isolated with the Histopaque method. The levels of poly(ADP-ribosyl)ated proteins were determined by Western blotting. The amount of reactive oxygen species was quantified by the OxyBlot method. To examine whether PARP activation continues to increase ex vivo in the leukocytes, blood samples were incubated at room temperature or at 37°C for 3 h with or without the PARP inhibitor PJ34. To investigate whether the plasma of burn/smoke animals may trigger PARP activation, burn/smoke plasma was incubated with control leukocytes in vitro. The results show that burn and smoke injury induced a marked PARP activation in circulating leukocytes. The activity was the highest immediately after injury and at 1 h and decreased gradually over time. Incubation of whole blood at 37°C for 3 h significantly increased poly(ADP-ribose) levels, indicative of the presence of an ongoing cell activation process. In conclusion, PARP activity is elevated in leukocytes after burn and smoke inhalation injury, and the response parallels the time course of reactive oxygen species generation in these cells.

[Inhalation injury--epidemiology, diagnosis and therapy]

OBJECTIVE

Inhalation injury is a vitally threatening medical syndrome, which might appear in patients with or without burn injuries. Thus, knowledge about development, diagnosis and treatment of inhalation injury should be available for each physician working in an intensive care unit.

METHODS

This review starts with the causal and formal pathogenesis of inhalation injuries. Furthermore, diagnosis and treatment in the critical care setting are presented, followed by the discussion of possible complications. Specific intoxications such as carbon monoxide are due to their importance separately discussed.

CONCLUSIONS

Inhalation injury present with an attributable excess mortality and thus worsen the prognosis of burned patients. New insights into the pathogenesis of inhalation injury, however, have led to improved therapeutic possibilities with improved outcome. Necessary prerequisites are a timely diagnosis and restrictive volume management, especially in patients with extensive burns. Prospective studies are needed to be able to answer the many emerging questions.